Various systems for utilizing existing telephone lines and power lines for carrying data from numerous locations for collection at a remote location point are known. Such systems are economically advantageous as they are able to utilize the existing infrastructure of these transmission media which extends to a significant portion of all the residential and business locations in the United States. However, the utility of the previously proposed systems is limited by the conflicting use of the lines for the existing purposes such as voice communications for the telephone network. Therefore, previous low cost systems have failed to provide the capacity to do demanding real time applications which cannot operate effectively using normal dial up procedures. An example of such a real time application is demand recording from utility meters. An additional problem with such previously known systems in real time applications is that the existing line must be released on demand for the existing use. For example, when the customer picks up his telephone to place a call the line must be made available to the customer. The present invention overcomes these limitations by utilizing the beneficial aspects of existing communications lines and telephone access while allowing access to the customer's location in a manner which does not affect existing uses for the existing communications line.
The present invention takes advantage of the structure of existing telephone lines. Existing lines are designed to preferentially pass only signals in the 300-3500 Hz frequency range which are audible on conventional telephone instruments. Existing telephone lines are run from the central office switch to a local distribution point known as a telephone company interface box (also referred to as a telephone pedestal or telephone vault) within which each individual pair is connected to the two-wire "loop" to the subscriber's house. A number of telephone lines fan out from the telephone company interface box to individual residences in a given neighborhood. The telephone interface box is typically within two thousand feet of each of the residences it serves, and within a few hundred feet in a great many cases. In every case, however, it lies between the residence and the telephone switch through which conventional calls must pass on their way to or from the residence. The telephone interface box typically has no power supply as the phone system works on power supplied by batteries associated with the switch.
The central office switch is an elaborate and expensive computerized device which permits any telephone on the system to be connected to any other. There is a separate, identifiable pathway from each numbered connection on the switch to a corresponding subscriber's telephone. From the 10,000 numbered connections on a typical switch, large bundles ("trunks") of individual lines disperse to the various neighborhoods served, each line ("pair") destined for a given subscriber's instrument. In each neighborhood the individual pairs in a trunk then enter a telephone company interface box.
The present invention utilizes the switched phone network to interface with an apparatus located at the telephone company interface box or other local distribution point to allow large numbers of customer locations to be rapidly accessed without the burdensome overhead of the switch while still maintaining the low cost benefits of the existing phone network. The present invention also provides for information access without interference with existing communication uses by utilizing normally attenuated out-of-band frequencies for communications over the relatively short distances between the local distribution point and the customer locations. The present invention further permits information access while telephone service is disconnected (cut-off at the switch). The present invention also avoids the problems which frequent telephone number reassignments cause previous systems which require a telephone call to be placed to each customer location.
To provide an economically feasible apparatus for communicating information between individual residential or commercial locations and remote locations it is an object of the present invention to take advantage of the infrastructure of existing communication lines such as telephone lines or cable lines. Furthermore, to allow such a system to operate in a real time or on demand mode, it is an object of the present invention to provide an apparatus which is designed to operate independently of the existing uses for the line to allow simultaneous use of the existing communication lines for their present purpose as well as for either bidirectional or unidirectional information exchange.
It is an object of the present invention to provide an apparatus for automated acquisition of one or more of a customer's utility meter readings using the customer's telephone line.
It is a further object of the present invention to provide an apparatus which may be used to collect readings from one or more meters or other devices at one or more customer locations.
It is a further object of the present invention to provide a method for customer information communication between a customer and a requesting location over existing communication lines.
It is a further object of the present invention to provide a method for communication of customer information even while voice service is disconnected.
It is a further object of the present invention to provide a method of reducing the cost of maintaining a data communications link with a given location even though the telephone number of that location may be frequently changed.
It is a further object of the present invention to provide a method for automated utility meter reading over a telephone line of a customer regardless of whether a request is received from a remote location.